The present invention relates to a support system for data migration suitable for providing support for efficiently migrating data from an old storage device to a new storage device and removing the old storage device within a computer system, particularly in a large-scale computer system, to which a plurality of storage devices are connected, a data migration support program, a method for identifying such a removable storage device, and a system for migrating data with a removable storage medium.
In an information system that handles a large amount of data, the capacity of a storage device for data storage needs to be large. The storage device capacity can be increased either by enlarging the size of an employed storage device or by using a large number of storage devices.
If it is anticipated that the stored information might be lost due to prolonged use of a storage device for a period longer than the estimated lifetime or if the storage device's defect detection rate is increased, the storage device is replaced with a new one that is less likely to deteriorate or become defective. Before the existing storage device is replaced, the data stored in it is transferred to another storage device. This transfer is called “data migration.” The same is also true for optical disks and other storage media.
A generally employed data migration method is to back up the data on an existing storage device to a tape or other storage medium and then restore it to a new storage device. To make such a backup, it is necessary to halt a host computer's access to the existing storage device. If the existing storage device has a large capacity, the resulting access halt time for backup is long.
In a situation where the old existing storage device and a new migration destination storage device are connected to the host computer via a network, data migration can be achieved, for instance, by allowing individual users using the existing storage device to copy necessary data to the new storage device before the old storage device is replaced by the new storage device. For example, the storage devices disclosed by Japanese Patent Laid-open No. 2000-187608 accomplish data migration between the old and new storage devices on an individual file basis and without intervention of a host computer. U.S. Pat. Ser. No. 6,108,748 disclosed a migration destination storage device, which uses a table that indicates whether data elements are migrated. When a host computer issues a transfer request about one or more data elements, the disclosed migration destination storage device judges whether the data elements are already migrated. If the data elements are already migrated, the migration destination storage device responds to the transfer request. If, on the other hand, the data elements are not migrated, the migration destination storage device migrates the data elements, responds to the transfer request, and writes into the table to indicate that the data elements are now migrated. While there are no services or requests, the migration destination storage device migrates data elements in the background. Thus, data migration requests can be fulfilled immediately.